The present invention relates to an “alternate imaging mode” for processing print jobs. It finds particular application in conjunction with multipitch, multipass marking architectures that accumulate composite page images on an intermediate substrate and subsequently transfer the full page image to a target substrate, and will be described with particular reference thereto. However, it is to be appreciated that the present invention is also amenable to other like applications
The terminology “copiers,” and “copies,” as well as “printers” and “prints,” is used alternatively herein The terminology “imaging” and “marking” is used alternatively herein and refers to the entire process of putting an image, film a digital or analog source, onto a target substrate (e.g., paper). The image can then be permanently fixed to the target substrate by fusing, drying, or other means. It will be appreciated that the invention applies to multipass, multipitch marking architectures in any type of digital print system, including, but not limited to systems in the fields of incremental printing of symbolic information, photocopying, facsimile, and electrophotography. Digital print systems are also referred to by many technical and commercial names within these fields, including: electrophotographic (e.g., xerographic) printers, copiers, and multifunction peripherals; digital presses; laser printers; and ink-jet printers
Digital print systems include paths through which sheets of a target substrate that are to receive an image are conveyed and imaged (ie., the paper path) The process of inserting sheets of the target substrate into the paper path and controlling the movement of the sheets through the paper path to receive an image is referred to as “scheduling”
One type of a multipass marking architecture is used to accumulate composite page images from multiple color separations. On each pass of the intermediate substrate, marking material for one of the color separations is deposited on the surface of the intermediate substrate until the last color separations is deposited to complete the composite image. Another type of multipass marking architecture is used to accumulate composite page images from multiple swaths of a print head On each pass of the intermediate substrate, marking material for one of the swaths is applied to the surface of the intermediate substrate until the last swath is applied to complete the composite image Both of these examples of multipass marking architectures perform what is commonly known as “page printing” once the composite page image is completed by transferring the full page image from the intermediate substrate to the target substrate.
Multipass printing may be scheduled in what may be referred to as “burst mode.” When scheduling in “burst mode,” sheets are inserted into, imaged, and output from the paper path at the maximum throughout capacity of the print system without any “skipped pitches” or delays between each consecutive sheet A “pitch” is the portion (or length) of the paper path in the process direction which is occupied by a sheet of the target substrate as it moves through the paper path. A “skipped pitch” occurs when there is a space between two consecutively output sheets which is long enough to hold another sheet. Various methods for scheduling in “burst mode” are disclosed in U.S. Pat. No. 5,095,342 to Farrell et al. and other patents. However, these patents are directed toward scheduling problems regarding duplex printing and integration of print engines with finishing devices, rather than the problems described herein and others which the present invention overcomes
In a multipitch marking architecture, the surface of the intermediate substrate (e.g., intermediate transfer drum or belt) is partitioned into multiple segments, each segment including a full page image (i.e., a single pitch) and an inter-document zone For example, a two pitch drum is capable of printing two pages during a pass or revolution of the drum. Likewise, a three pitch belt is capable of printing three pages during a pass or revolution of the belt In a multipitch, multipass marking architecture, traditional “burst mode” scheduling starts accumulating images for each pitch of the intermediate substrate at the beginning of a print job and on the final pass of the multipass cycle each composite image is transferred to a target substrate
However, problems can arise when attempting to transfer multiple composite images from the intermediate substrate (e.g., intermediate transfer drum or belt) to the target substrate (e.g., paper) during the same pass These problems are primarily associated with integration of the intermediate substrate/transfer station with adjacent stations (e.g., preheating or other type of pre-conditioning stations and fusing stations) in the paper path. This is particularly a problem in a high-speed print system. For example: i) preceding stations (e.g, preheating or pre-conditioning stations) may not be able to operate properly if the target substrate is advanced at the same speed as in the transfer station, ii) likewise, successive stations (e.g., fusing stations) may not be able to receive the transferred sheets as fast as the transfer station can output them, iii) alternatively, to make the adjacent stations capable of such operation they may become unacceptably large and/or economically cost prohibitive. Furthermore, registration of sheets in the paper path to the composite page images on the intermediate substrate may not be sufficiently reliable if it is performed at the same speed as sheets advancing through the transfer station.
Accordingly, there is a need for an alternative to traditional “burst mode” scheduling for multipitch, multipass marking architectures that accumulate full page images on an intermediate substrate. The present invention contemplates an “alternate imaging mode” that overcomes the above-referenced problems and others.